1. Field of the Invention
This invention relates generally to optical and electronic bonding equipment and more particularly to bonding equipment for precisely aligning and placing optoelectric components on substrates.
2. Description of the Related Art
Precise alignment of surfaces in the placement of optoelectric components on substrates has received much attention. This is particularly true in VLSI circuit elements where the patterning of the circuit is microscopic or nearly microscopic. Many small components are typically bonded to these circuits. The problem with placing these small components with high precision, i.e. within microns, is accurately locating and correlating the component and placement position. Also, the component must be moved to the exact placement position without error.
The prior art has done this by moving the component over an uplooking visible light camera and the substrate under a downlooking visible light camera. A series of pictures are taken and the two images correlated. Corrections are made by the mechanical system to place the component over the substrate and the two are brought tog, ether. The difficulty in this prior art is that after the component and substrate are located by the cameras and vision system, they must be moved horizontally and vertically which introduces errors into the system. The greater the distance the component and substrate have to move, the greater is the alignment error that results from the smallest imprecision in the mechanical system's machined parts.
Another method employed is to position the component over the substrate and place a thin optical probe between them as in U.S. Pat. No. 4,899,921 to Bendat et al. The mechanical system will maintain alignment of the component and substrate for as long as the probe fits between. At some point the probe must be removed and the component and substrate moved together. It is at this point alignment errors are introduced.